There have already been put on the market various display devices each of which is so designed that a display panel, for instance, a flat display panel such as a liquid crystal display panel or an organic EL panel is provided with a tablet plate to thus permit the input of information such as characters and/or patterns through handwriting using, for instance, a data-inputting device such as a data-inputting pen and that the contents thus inputted into the device can be displayed on the display panel.
The display device is provided with a transparent protective plate on the side of the device facing the observer in order to maintain the desired display quality thereof while eliminating the occurrence of any local pressure possibly applied onto the same when inputting information into the device (see, for instance, FIG. 3 attached to Patent Document 1 or FIG. 1 attached to Patent Document 2). In this respect, a glass plate has preferably been used as such a protective plate in the light of the excellent characteristic properties thereof such as high mechanical strength, good weatherability and high light-transmittance.
It has been required for the foregoing display devices to increase the area thereof for the display and to reduce the weight thereof for its portable use and it has correspondingly been required for the protective glass plate used in the foregoing display devices to increase the area thereof and to reduce the thickness of the plate for the reduction of the weight thereof.
Patent Document 1: Japanese Un-Examined Patent Publication Hei 6-75213;
Patent Document 2: Japanese Un-Examined Patent Publication 2004-240548